A long time I was angry that my iMac is relatively slow when multiple programs are running simultaneously - the installation of PSE made this particularly clear. So memory upgrade. After studying the Amazon reviews (in terms of quality of the modules) I have chosen the Kingston (also because the dealer returned to A) - according to the comments to take the manufacturers anything. I chose to the basic version of the iMac plus 2x4GB because I mean that 12 GB are quite sufficient and also because is the limiting component for the speed of a Mac not only the memory. Also, I did not need me to deal with the pulling out of the two installed 2x2 GB modules (sitting really tight) but had only the two new reinzuschieben (down left and right with your thumb and already made it 'click').
The installation (already well described in the iMac Handbüchlein that came with the device - in my opinion better than the Internet) was in less than 10 minutes occurred (the three screws holding the cover could easily be solved). The date slowest startup programs (PSE and Word) are much faster 'because'.
